Sold by the Undead Male Merchant for 600 souls.
told you :/. I don't suggest using it until you at least +10 it.
+15 it if you don't want to imbue it
also
black knight sword best sword 2k15

Where do i find black knight sword?

farm black knights who wield the black knight sword
get item discovery gear
and kill the black knight in undead asylum
and the one near the third or so bonfire
and the other ones
also
seriously
you are a pleb
google this shit for gods sake

Yes it is found by the merchant


You find any of the black knight weapons by fighting a black knight that has the desired weapon and hope he drops it. You can increase these chances by having ten humanity and the chest head thingy or the ring. Im pretty sure they dont stack (at least one doesnt). You can find a black knight with the small sword in a couple different places, the closest being in undeadberg near the tower where you fight havel and the 2nd boss (taurs demon?)

Some other items to consider:

Black knight halberd (not really what you are looking for, but has some amazing damage)

If you kill Sif you can use his soul to make artoris great sword, which is a amazing weapon

And some other stuff.

I'd really not suggest for him to use the black knight halberd at his level. It has a really trash moveset, and requires quite a lot of practice with dodging, riposting, blocking, and shit like that to properly utilize it.

So what do you think is the best weapon for killing a boss quickly?

A weapon doesn't make the game easier, learning how the game functions does. This isn't a game where you can just get a decent weapon and faceroll the game, you have to really think and understand every mechanic to excel.

It all depends how good a player you are. If you don't want to learn and just want to win easy then rapier or something similar with a fast move set is best. You don't have to learn boss patterns because you will always have stam left to roll, and you don't need to learn timings because your attacks are so fast.

If you want to kill bosses fast then using big slow strong weapons is much better, but because the attacks are slow and use a lot of stam you need to be a lot more wary. Zweihander, dragon ultra great sword and black knight halberd are all great at melting bosses, but if you don't know what you are doing then you will be caught with no time to react and no stam to roll.

Having a strong weapon can compensate for lack of skill, but in the end just learn to play the game, it's overhyped and really not that hard... For me I prefer naked zwei + grassblade sheild most of the time. You can get both very early in the game, and you can easily stay underweight (<12.5% is optimal) and maintain damage.

Every boss has their own strengths and weaknesses, there is no single enchantment that will beat them all, so it's best to stick with normal path weapon and use buffs to match their weaknesses.

if you don't want to pvp
then just use the fucking dragon sword
that shit rapes easily

Its really not. The range makes it super safe for new players. I would know, I used it as a new player, had 0 problems with it.